We know that the realization of PLC functions is largely realized by its integrated IO interface. Among all kinds of IO, digital input and output IO is the most common, and every PLC will be integrated. You may have heard of the so-called PNP IO and NPN IO. What is the difference between them? Simply put.

Regardless of whether it is a PNP type IO or an NPN type IO, the triode inside is brown to the positive pole, blue to the negative pole, and black to the signal. The PNP triode is connected to the brown positive pole and the black signal, and the NPN triode is connected to the blue negative pole and the black signal. Therefore, the PNP type IO controls the on-off through the positive pole, and the NPN type IO controls the on-off through the negative pole. We should choose the most suitable digital input and output IO according to the needs of the project to achieve twice the result with half the effort.

The PLC produced by our company supports codesys programming and supports the expansion of various IO interfaces.